So that should mean my 12Hydro will already have 100 lbs more than my 12 G and directly on the rear axle as well. Which also means the hydro driven by my boys will have the same final weight as the 12 gear driven by me.

That ALSO firmly decides which of the two tractors will be need to have it's wheels removed to be put in the back of my pickup (has a cap/topper) and which will remain intact and will drive onto the trailer on it's own power!!